Diesel oxidation catalysts (DOCs) reduce the amount of carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas by oxidizing them to carbon dioxide and water.
2 CO + O2 → 2 CO2
CxHy + (x+y/4) O2 → x CO2 + (y/2) H2O
The oxidation of NO to NO2 is another important function of DOCs, enabling a faster reduction of NOx with NH3 on the downstream SCR technologies when NO2 is present.
2 NO + O2 → 2 NO2